On Wed, 31 Aug 2011 10:41:49 +0530
Rajan Aggarwal <rajan.aggarwal85@xxxxxxxxx> wrote:
> The bdi_writeback_thread function does not use spin_lock to
> see if the work_list is empty.
>
> If the list is not empty, and if an interrupt happens before we
> set the current->state to TASK_RUNNING then we could be stuck in
> a schedule() due to kernel preemption.
>
> This patch acquires and releases the wb_lock to avoid this scenario.
>
> Signed-off-by: Rajan Aggarwal <rajan.aggarwal85@xxxxxxxxx>
Hmm, even if it sleeps, bdi_wakeup_flusher() will wake up the thread.
But it seems there is an useful function schedule_timeout_interruptible().
Then, how about this ? Your concern will go away with this ?
==
>From 5558d23b72004a890dc37411aa7515996c8592fa Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Thu, 1 Sep 2011 17:02:13 +0900
Subject: [PATCH] use schedule_timeout_interruptible() in bdi_writeback_thread
Use schedule_timeout_interruptible() rather than
set_current_state(TASK_INTERRUPTIBLE);
do some work
schedule_timeout()
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 22 +++++++++-------------
1 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 04cf3b9..c538bda 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -936,22 +936,18 @@ int bdi_writeback_thread(void *data)
if (pages_written)
wb->last_active = jiffies;
- set_current_state(TASK_INTERRUPTIBLE);
- if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
- __set_current_state(TASK_RUNNING);
+ if (!list_empty(&bdi->work_list) || kthread_should_stop())
continue;
- }
+ /*
+ * If we have nothing to do, we can go sleep without any
+ * timeout and save power. When a work is queued or
+ * something is made dirty - we will be woken up.
+ */
+ timeout = MAX_SCHEDULE_TIMEOUT;
if (wb_has_dirty_io(wb) && dirty_writeback_interval)
- schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
- else {
- /*
- * We have nothing to do, so can go sleep without any
- * timeout and save power. When a work is queued or
- * something is made dirty - we will be woken up.
- */
- schedule();
- }
+ timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ schedule_timeout_interruptible(timeout);
try_to_freeze();
}
--
1.7.4.1
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